Researchers find path to 'unlimited solar power'

Posted: 12 November 2008

Author: Ann Steffora Mutschler

In what Massachusetts Institute of Technology (MIT) researchers say is a revolutionary leap that could transform solar power from a marginal, boutique alternative into a mainstream energy source, the researchers report they have discovered a way to store energy for use when the sun doesn't shine, thereby overcoming a major barrier to large-scale solar power. This report from Electronics Weekly is published with an added commentary by energy guru Walt Patterson.

Daniel G. Nocera
Daniel G. Nocera
Daniel G. Nocera, the Henry Dreyfus Professor of Energy at MIT, has developed a simple method to split water molecules and produce oxygen gas, a discovery that paves the way for large-scale use of solar power. Photo © Donna Coveney
Until now, solar power has been a daytime-only energy source, because storing extra solar energy for later use is prohibitively expensive and grossly inefficient, but MIT researchers have come upon a simple, inexpensive, highly efficient process for storing solar energy that requires nothing but abundant, non-toxic natural materials, inspired by the photosynthesis performed by plants.

"This is the nirvana of what we've been talking about for years. Solar power has always been a limited, far-off solution. Now we can seriously think about solar power as unlimited and soon," noted MIT's Daniel Nocera, the Henry Dreyfus Professor of Energy at MIT and senior author of a paper describing the work in the July 31 issue of Science, in a statement.

Nocera and Matthew Kanan, a postdoctoral fellow in Nocera's lab developed a process that will allow the sun's energy to be used to split water into hydrogen and oxygen gases, which later may be recombined inside a fuel cell, creating carbon-free electricity to power houses or electric cars, day or night.

Key component

The key component in the process is a catalyst - cobalt metal, phosphate and an electrode, placed in water - that produces oxygen gas from water (pictured below), while another catalyst produces hydrogen gas.

When electricity - whether from a photovoltaic cell, a wind turbine or any other source - runs through the electrode, the cobalt and phosphate form a thin film on the electrode, and oxygen gas is produced, the researchers explained.

Combined with another catalyst, such as platinum, that can produce hydrogen gas from water, the system can duplicate the water splitting reaction that occurs during photosynthesis.

Storing solar energy
Storing solar energy
MIT researchers have developed a new catalyst, consisting of cobalt metal, phosphate and an electrode. When the catalyst is placed in water and electricity runs through the electrode, oxygen gas is produced. When another catalyst is used to produce hydrogen gas, the oxygen and hydrogen can be combined inside a fuel cell, creating carbon-free electricity to power a house or an electric car, day or night. Photo © Tom White, MIT
The new catalyst works at room temperature, in neutral pH water, and is easy to set up, Nocera said. "That's why I know this is going to work. It's so easy to implement," he said.

'Major discovery'

Nocera also said that sunlight has the greatest potential of any power source to solve the world's energy problems, since in one hour, enough sunlight strikes the Earth to provide the entire planet's energy needs for one year.

"This is a major discovery with enormous implications for the future prosperity of humankind. The importance of their discovery cannot be overstated since it opens up the door for developing new technologies for energy production thus reducing our dependence for fossil fuels and addressing the global climate change problem," added James Barber, a leader in the study of photosynthesis, the Ernst Chain Professor of Biochemistry at Imperial College London. He called the discovery a "giant leap" toward generating clean, carbon-free energy on a massive scale.

While this is a good start, the currently available electrolyzers that split water with electricity and are often used industrially, are not suited for artificial photosynthesis because they are very expensive and require a highly basic (non-benign) environment that has little to do with the conditions under which photosynthesis operates, Nocera said.

More to do

As such, more engineering work needs to be done to integrate the new scientific discovery into existing photovoltaic systems, but Nocera is confident that such systems will become a reality.

"This is just the beginning. The scientific community is really going to run with this," he added.

Nocera hopes that within 10 years homeowners will be able to power their homes in daylight through photovoltaic cells, while using excess solar energy to produce hydrogen and oxygen to power their own household fuel cell. Electricity-by-wire from a central source could be a thing of the past.

The project is part of the MIT Energy Initiative, a program designed to help transform the global energy system to meet the needs of the future and to help build a bridge to that future by improving today's energy systems.

Ann Steffora Mutschler is Senior Editor - Electronic News, a daily newsletter from Electronics Weekly

COMMENT: Exciting possibility

Walt Patterson,author of Keeping The Lights On: Towards Sustainable Electricity comments:

Calling this 'photosynthesis' seems to me a bit odd, indeed actively misleading. It seems to be catalyzed photolysis, which is not 'synthesis' of any kind - quite the opposite, in fact.

The key distinction is between electrolysis and photolysis. The concept of electrolysis, using renewable electricity to split water intohydrogen and oxygen, has been around for decades, but too costly and complicated. I myself was actually asked, at least seven years ago, whether I'd like to have an experimental solar electrolyzer and fuel cell on our little house in Greece. Although it did not happen, it was a genuine inquiry, from a senior executive who considered it feasible.

If the process is just electrolysis, I hope the MIT scientists involved > did not claim this as a 'new' idea, because it's not. The story, however, seems to imply direct photolysis - using sunlight itself to split water molecules. If so, that would be new, and exciting - depending on the catalysts, the rate of reaction and other practical details.